a mall emo is a person who fits the "emo" cliche (long greasy black fringe, tight lady black jeans, guyliner/heavy eyeliner, etc) who hangs about the mall listening (loudly) to "emo" music and moping about and just being "emo".

Normal person: Whoa! Check out the flocks of mall emo kids!
Other normal person: There everywhere!
Family Guy Fan: THERE IN MY RACOON WOUNDS!!